Here is the way I do mine and it seems to work out well. First have the trim control as low as it will go on the transmitter and the throttle at low. Set the servo arm so that it just closes the throttle barrel as far as it will go without any binding. Now set the throttle travel so that when the throttle lever is fully advanced, the throttle barrel just reaches it's limit. You may have to experiment a bit with the length of the servo arm to achieve these settings by moving in or out from the servo pivot point. Now, when you start the engine, you have to have the throttle trim open a bit, probably at about center position; just adjust for proper idle with the throttle lever at low. Now, you should be able to kill the engine when you move the throttle trim to low; a desirable thing to be able to do.